[c-nsp] 6500 iBGP mesh

[Francois Corthésy]

Might I point out that it seems the Sup32/Sup720 line (except for the 
Sup720-3BXL) have a limitation based on their forwarding chip to about 
239K routes.
I'm no guru, but this was pointed out in a thread earlier on and sadly 
confirmed through a Cisco TAC.
Earlier discussion : 
https://puck.nether.net/pipermail/cisco-nsp/2006-August/032814.html

Francois

Bruce Pinsky wrote:
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> Aubrey Wells wrote:
>   
>> Hello,
>> We currently have two iBGP peered edge routers that are eBGP peered to 
>> several upstreams, as well as several private peering arrangements. 
>> These two routers are in seperate data centers connected via a Layer-2 
>> ethernet circuit. Downstream from the edge routers is a mesh of 
>> Sup2/MSFC2 6506s that are aggregate points for many other POPs. All 
>> devices are connected via IGP (ospf). Currently, when a customer route 
>> gets to an edge router, it looks up the destination in the table and 
>> sometimes has to send the packet over the layer2 circuit to the other 
>> edge router. Since all traffic at some point goes through a 6500, I 
>> would perfer to have the 6500 make the decision of which edge router to 
>> go to for the route, saving me the bandwidth on the L2 interconnection 
>> between the edge routers, and eliminating a hop for the customer.
>>
>> My thoughts on solving the problem is to set up a iBGP mesh between the 
>> 6500s and the edge routers so any one route will (almost) never hit both 
>> edge routers. Will the Sup2 be able to handle a full view from each edge 
>> router to accomplish my goal? Any suggestions to make it work (outside 
>> of upgrading to Sup720)?
>>
>>     
>
> I know of a customer that has two full views at about 210K+ routes.  That's
> about 170MB of BGP usage.  Depending on which image you are running on the
> Sup2 and if you have 512MB of memory, you should be pretty good.  If you
> have 256MB you are probably pushing the envelope on the amount of free
> memory headroom you have.  Less than 256MB, well, "that dog don't hunt."
>
> One option would be to use another device in the network as a non-transit
> route reflector to have a single peering connection between your 6500's
> with Sup2 and the RR.  Downside to that is that you have a single point of
> failure now instead of having two independent BGP sessions to the
> edge/border routers.  And of course adding a redundant RR would put you
> right back in the same position as you started.   You'd have to decide
> which is more important, the single point of failure or the bandwidth
> between the edge routers.
>
> - --
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